Light Emitting Diode (LED) lamps are solid state devices that emit light with high efficiency. However, they do not survive high operating temperatures above 120 C, and their efficiency and reliability drop drastically as their temperatures rise above 80 C. In comparison, an incandescent lamp operates successfully above 1200 C. Accordingly, heat dissipation from LEDs is an important problem to address in order to insure long life, reliability, and efficient operation of LED lamps.
A conventional conduction heat sink that consists of a relatively heavy piece of metal with high thermal conductivity, such as aluminum or copper, sometimes having air cooled fins, is marginally applicable for low intensity LED lamps, while high intensity LEDs need more efficient cooling methods such as liquid cooling or heat pipe cooling.
Liquid cooling of electronic components is well known, as taught in U.S. Pat. No. 6,055,154, wherein the back of an electronic chip is exposed to a current of cooling fluid moved by a pump. The concept of liquid cooling by impingement of water jets against the back of a heat sink is shown in U.S. Pat. No. 5,316,075. Although quite effective, liquid cooling requires the use of coolant pumps, controls, blowers or fans, and is therefore quite expensive.
Cooling using a phase change process, such as by using a heat pipe, is also known, as taught in U.S. Pat. Nos. 7,210,832; 6,926,072; 6,910,794; 6,474,074 and others. The connection of a hot chip to a heat pipe is an application in central processing unit (CPU) cooling found in many modern computers. However, most heat pipes have an internal wick structure that is expensive to manufacture and can only be justified in the cooling of high cost electronics such as CPUs. Moreover, heat pipes fail if there is a leakage of their working fluid.